Instantaneous Torque Control of Magnetically Suspended Reaction Flywheel

With the requirement of spacecraft attitude control accuracy, the reaction flywheel is demanded deliver higher precision torque. To improve the torque-output precision of the magnetically suspended reaction flywheel, a new torque control method is proposed. First, comprehensive analysis of torque ripple of brushless DC motor (BLDC) due to commutation and inactive phase diode freewheeling is presented. Second, in order to eliminate the diode freewheeling of the inactive phase, the modulation PWM_ON_PWM pattern is adopted. Third, compensation methods to attenuate the commutation torque ripple by modulating the switching-in phase during low-speed region and modulating switching-out phase during high-speed region are given. Upon this, calculation method of the commutation time is introduced. Finally, the experimental results show that the proposed methods can eliminate both commutation and non-commutation torque ripple efficiently.